The companies have been working with the World Wildlife Fund (WWF) and the World Resources Institute (WRI) to draw up the guidelines, with the WWF's senior vice president for private sector engagement Suzanne Apple claiming the principles 'provide sound guidance to the market providers'.

"These companies are leading the market in creating demand for renewable energy," said Apple. "Some of America's largest companies are embracing renewable energy, and their collective demand requires the market to keep pace."

"The Renewable Energy Buyers' Principles are a powerful way to bring energy suppliers and consumers together, enabling us to work creatively to maximize the inherent benefits that come from clean energy generation with more predictable costs."

Limited options

The high demand for renewable energy has led to major businesses actively adding renewable energy plants on-site, with 60% of the largest US firms setting public climate change and energy goals. The signatories state that billions of kilowatt hours are still needed to meet their renewable energy targets and that businesses still face huge challenges accessing cost-effective projects to reduce carbon emissions.

Sprint's director of corporate responsibility and sustainability Amy Hargroves said: "We know cost-competitive renewable energy exists but the problem is that it is way too difficult for most companies to buy.

"Very few companies have the knowledge and resources to purchase renewable energy given today's very limited and complex options. Our hope is that by identifying the commonalities among large buyers, the principles will catalyse market changes that will help make renewables more affordable and accessible for all companies."

The Buyers' Group will form an informal consortium of companies interested in sharing best practices and helping businesses buy renewable energy, with the aim of expanding beyond the 12 starting signatories as more companies recognise the need for market change to seize the opportunities around renewable energy.